The present invention relates to a transfer apparatus for conveying a long material, e.g. a photographic film, which has physical markers provided thereon at equal intervals.
In a common transfer apparatus, a long material such as a photographic film is transferred by the rotating action of rollers. The rotating action of the rollers can be controlled with the use of a servo motor or a stepping motor. However, a transfer movement of the long material is not always constant and instead may be varied.
This results from variations in the movement and configuration of the rollers or other components, friction loss between the material and the rollers, and weariness of the rollers and components after a long period of service.
Some of the errors may be eliminated at a manufacturer factory before shipment but the remaining including time-dependent errors should be corrected on site as necessary.
In general, the correction is made by measuring an actual movement of a test piece with a scale, comparing it with a predetermined reference movement to calculate a difference, producing a correction factor from the difference, and correcting the actual movement with the correction factor.
For ease of measuring the actual movement, scores or markings are prepared on the test piece.
The above method of correction however has some disadvantages as explained below.
For the measurement of the actual movement, a test piece of the long material or film has to be subjected to the transfer action which thus increases the consumption of time.
There must be measurement variations of the test piece depending on the precision of the scale or the skill of an operator. This will result in lower accuracy of the correcting action.
As the correction factor is manually calculated by the operator comparing the actual movement with the predetermined reference movement to determine a difference, the overall correcting action will hardly be expedited.
The calculation by the operator may be mistaken thus yielding a fault correct factor.
The correcting of the actual movement to the reference movement using the correction factor is also carried out by a manual control of the apparatus and thus lowers the efficiency.
For the same reason, the correcting of the actual movement may hardly be executed without failure of entry of the correction factor but in perfection.
As the test piece of the long material or film has to be used for the trial measurement, the transfer action declines in efficiency.
As the test piece is provided with scores or markings for the measurement, it will not be substituted with a negative film to be printed.
Above all, the conventional method of correction includes a number of troublesome steps which are not pleased by the operator and will hardly contribute to the efficient operation of the apparatus.
It is an object of the present invention to provide an improved transfer apparatus capable of conveying a long material such as a negative film without the use of a test piece and with no need of manual calculation of a correction factor.